Method and means for stabilizing soaps



Patented May 28, 1940 m'rso s'rrss PATENT OFFICE Lauren B.

Hitchcock and Robert E. Divine,

Niagara Falls, N. Y., assignors to Hooker Electrochemical Company, New York. N. Y., a corporation or New York No Drawing. Application October 14, 1937,

Serial N0. 168,994

15 Claims.

The deterioration of soap is due principally to atmospheric oxidation and therefore proceeds from the outer layer inward. This oxidation produces what is known as rancidity. Rancidity results in offensive odor and discoloration. Oxidation and discoloration are promoted by sunlight, warmth and humidity, especially in the presence of metals, which have a catalytic effect upon oxidation.

Iron, manganese and copper are the metals most commonly found in soap. They are introduced through the caustic soda as well as through the fats or fatty acids used in production of the soap. Caustic soda low in metal content is now commercially available; nevertheless it is still necessary or desirable to use a stabilizing agent to retard deterioration. Among the agents in common use are diphenylamine, sodium hyposulphite (Nazszor) and sodium thiosulphate (Na-28203). In Calcott Patent No. 1,993,771 there is also disclosed the possibility of using such materials as p-hydroxy-diphenyl,o-hydroxy-diphenyl, di-p-p-hydroxy-dipheny1, beta-naphthylpara-phenol, 2,7-di-hydroxy-naphthalene etc. for this purpose. All of these are antioxidants. The two containing sulphur also have the property of converting the metals present to their sulphides, which renders them less active as oxidation catalysts. It has been customary to introduce these by incorporating them with the dry soap during the milling operation. When so introduced the particles of ground crystals and soap are of course enormous in size compared with the molecules of .the respective ingredients. The association of the agent with the molecules of soap is therefore not very intimate and the agent cannot develop its full effectiveness.

We shall hereinafter refer to stabilizing agents containing sulphur which they will readily give up to metals as sulphiding agents.

These sulphiding agents are inert with respect to caustic soda. We have discovered that the effectiveness of sulphiding agents is much increased if they are introduced into the caustic soda from which the soap is to be produced especially if they are soluble in caustic soda solution. The reasons for this are as follows:

When fats or fatty acids are saponified by a caustic alkali, boiled and allowed to stand, the products are found to separate into three layers. The uppermost of these, which is the purest, constitutes the neat soap. The next, called the nigre layer, is darker and contains impurities. The bottom layer consists of spent lye and glycerine. Any metals present are ordinarily found in all three layers, although not uniformly distributed as between them. We have found, however, that if a sulphiding agent be added to the reagents before or during saponification the metals tend to concentrate in the lower part of the nigre layer. that the sulphides are heavier than their metal soaps and other compounds usually formed, hence tend to settle more rapidly. The upper layer of the saponification products is therefore relatively free from metals. Other factors being equal, soap made in this way therefore is freer from catalytic metals than soap made by present methods. The sulphiding agents therefore act as metal precipitating agents. Moreover, as stated above, the sulphides remaining in the soap are less active as oxidation catalysts than their metals. The action of sulphiding agents if present during saponification is therefore two fold; namely, they reduce the quantity of metals in the soap and render those that remain relatively innocuous. If such agents be also antioxidants they act directly to protect the soap against oxidation and their action is therefore threefold.

Furthermore, if the stabilizing agents be soluble in the caustic soda solution they are brought into liquid phase and hence more uniform distribution and more intimate molecular association with the metals and soap than could possibly be the case when incorporated with the soap in dry form in accordance with the prior art. Whether the agents are antioxidants or sulphiding agents or both, their efiectiveness is thereby greatly increased. That is to say, if they are simply antioxidants their effectiveness as such will be enhanced. If they are sulphiding agents their effectiveness in reducing catalytic activity of the metals will be increased and in addition they will have increased effect in precipitating the metals. If they are both antioxidants and sulphiding agents their effectiveness will be increased in all three respects.

A further advantage of adding the stabilizing agent to the caustic soda solution results from the fact that it permits this to be done by the manufacturer of the caustic soda during the processing of the commercial solution, before its shipment to the soap manufacturer. The latter is thereby enabled to buy caustic soda solution already containing the agent and is thus spared the troublesome steps of grinding the agent and milling it into the soap.

The soap manufacturer could of course add the stabilizing agent to the caustic soda solution before reacting it with the fat, but this would in- This may be due to the fact Ill) process, 1. e., that in which the agent is milled into the dry soap.

Example 1 A batch of boiled soap was made up from tallow and cocoanut oil, in the proportions of 80 to per cent, by reaction with caustic soda to which 0.8 per cent of sodium thiosulphate, based upon the NaOH, had been added. Another batch was made up from identical reagents except that the thiosulphate was omitted. From the neat soap layers of these batches were formed the usual cakes by ordinary and identical processes, including the customary milling step. No stabilizing agent was added during the milling. Both batches were exposed to normal aging conditions. At the end of eight weeks cakes made from the first batch were notably whiter than those made from the second batch.

Example 2 A batch of boiled soap was made up like the first batch of Example 1 and a second batch was made up from identical reagents excepting that the sodium thicsulphate was omitted from the caustic soda and afterward added to the soap during the milling operation in accordance with ordinary practice. After a normal aging for a period of eight weeks the cakes made from the first batch were appreciably whiter than those made from the second batch.

Example 3 A batch of cold process soap was made up from cocoanut oil and caustic soda to which 0.8 per cent of sodium thiosulphate had been added. Another batch was made up from identical reagents except that no stabilizing agent had been added to the caustic soda. These batches were poured into cylindrical glass molds, from which they were removed as soon as hard. Both batches were subjected to normal aging conditions for ten weeks, at the expiration of which period the cylindrical cakes were cut into discs. The discs thus cut from the first batch were milk white on both their cylindrical exterior surfaces and on the freshly exposed fiat surfaces, no difference being distinguishable. The discs cut from the second batch were distinctly yellowed on their cylindrical surfaces in sharp contrast with the milky whiteness of the freshly exposed flat surfaces. This yellow'color extended inward to a distance of one-eighth to one-quarter inch.

Among the stabilizing agents that may be used in accordance with our invention, namely by incorporating them in the caustic soda solution before or during the saponifica'tion reaction, are the following:

1. Elemental sulphur (forms NazS and NaaSzOs etc.)

2. Hydrogen sulphide (HzS, forms sulphiding agent only, soluble).

3. Sodium sulphide (NazS, reducing anti-oxidant and sulphiding agent, soluble).

iiti

4. Sodium hydrosulphide (NaSH, forms M128).

5. Sodium sulphite' (Nazsoa, reducing antioxidant, soluble).

6. Sodium hyposulphite (Na2Sz04, reducing antioxidant and sulphiding agent, soluble).

7. Sodium thiosulphate (NaaSzOs, reducing antioxidant and sulphiding agent, soluble).

8. Any two or more of the above compounds used jointly or successively.

9. All alkaline earth or alkali metal analogues of the foregoing sodium compounds.

10. All double sodium and potassium analogues of the foregoing sodium compounds.

11. Mercaptans (anti-oxidants and sulphiding agents, soluble).

12. Sulphoxylates, such as NaHSOz (antioxidant and sulphiding soluble agents).

13. Any organic compound of the form R2S2O3, where R may be any alkali metal or any monovalent organic group, such as a hydrocarbon residue, either aliphatic or aromatic, substituted or not; for example, mono-, dior tri-alkylolammonium thiosulphate (antioxidant and sulphiding agents) 14. Componds of hyposulphites with aldehydes, such as hyposulphite formaldehyde or sulphoxylate formaldehyde (antioxidants only).

It should be noted that some of the above com pounds, such as the sulphites, are antioxidants only. Others, such as the sulphides and hydrosulphides, are sulphiding agents but not antioxidants. Their action is twofold. Still others, such as the hydrosulphites and thiosulphates, are antioxidants and also sulphiding agents. The agents which are both antioxidants and sulphiding agents are of course preferred, as their action is threefold. The hydrosulphides, hyposulphites and thiosulphates are especially desirable antioxidants, as they are active reducing agents.

We do not wish to be limited to the above list of stabilizing agents as it would appear that any water-soluble compound which will give up sulphur to metals, also any simple reducing antioxidant which can be dissolved in caustic soda solution, will be more or less suitable for my process.

The caustic alkali containing a stabilizing agent may be reacted with any suitable saponifiable carboxylic compound, including the usual animal and vegetable fats, fatty oils and fatty acids, such as tallow (glyceryl tristearate) lard, lard oil, palm oil, cottonseed oil and their fatty acids.

The word "so1uble as used in the above list and in the appended claims is to be understood as meaning soluble, at least to the extent that is essential for our purposes, in an aqueous solution of the caustic alkali of the highest concentration that will remain liquid at ordinary temperatures.

We claim as our invention:

1. The process for production of soap relatively free from metals tending to promote deterioration of soap which comprises saponifying a suitable fatty material by means of an aqueous solution of caustic soda, containing sensible quantities of such metals, in presence of a commensurate quantity of a sulphur compound which forms with said metals compounds that-are relatively innocuous with respect to soap as well as relatively insoluble and tend to settle in fluid soap, allowing the products to settle and sepa rate and removing the relatively metal-free upper or neat soap layer.

2. The process for production of soap relatively free from metals tending to promote deterioration of soap which comprises saponifying a suitable fatty material by means of an aqueous solution of caustic soda, containing sensible quantities of said metals, in presence of a commensurate quantity of an agent which readily gives up sulphur to said metals and forms with them compounds that are relatively innocuous with respect to soap as well as relatively insoluble and tend to settle in fluid soap, allowing the products to settle and separate and removing the relatively metal-free upper or neat soap layer.

3. The process for production of soap relatively free from metals tending to promote deterioration of soap which comprises saponifying suitable fatty material by means of an aqueous solution of caustic soda, containing sensible quantities of such metals, in presence of a commensurate quantity of an agent selected from the group consisting of the mercaptans and alkali metal sulphides, hyposulphites, thiosulphates and sulphoxylates, allowing the products to settle andseparate and removing the relatively metal-free upper or neat soap layer.

4. The process for production of soap relatively free from metals tending to promote deterioration of soap which comprises making up aqueous caustic soda, containing sensible quantities of such metals, said caustic soda having added thereto a commensurate quantity of a sulphur compound which forms with said metals compounds that are relatively innocuous with respect to soap and also relatively insoluble and tend to settle in fluid soap, reacting said caustic soda with a suitable fatty material, allowing the products to settle and separate and removing the relatively metal-free upper or neat soap layer.

5. The process for production of soap relatively free from metals tending to promote deterioration of soap which comprises making up aqueous caustic soda, containing sensible quantities of such metals, said caustic soda having added thereto a commensurate quantity of an agent which readily gives up sulphur to said metals and forms with them compounds that are relatively innocuous with respect to soap and also relatively insoluble and tend to settle in fluid soap, reacting said caustic soda with a suitable fatty material, allowing the products to settle and separate and removing the relatively metalfree upper or neat soap layer.

6. The process for production of soap relatively free from metals tending to promote deterioration of soap, which comprise making up aqueous caustic soda, containing sensible quantities of such metals, said caustic soda having added thereto a commensurate quantity of an agent selected from the group consisting of the mercaptans and alkali metal sulphides, hyposulphites, thiosulphates and sulphoxylates, reacting said caustic soda with a suitable fatty material, allowing the products to settle and separate and removing the relatively metal-free upper or neat soap layer.

7. As a new article of commerce, aqueous caustic soda, containing sensible quantities of metals normally having a tendency to promote deterioration of soap, which caustic soda when reacted with a suitable fatty material will nevertheless produce soap relatively free from such metals, said caustic soda having added thereto a commensurate quantity of a sulphur compound which forms with such metals compounds that are relatively innocuous with respect to soap as well as relatively insoluble and tend to settle in fluid soap.

8. As a new article of commerce, aqueous caustic soda, containing sensible quantities of metals normally having a tendency to promote deterioration of soap, which caustic soda when reacted with a suitable fatty material will nevertheless produce soap relatively free from such metals, said caustic soda having added thereto a commensurate quantity of an agent which readily givesup sulphur to such metals and forms with them compounds that are relatively innocuous with respect to soap as well as relatively insoluble and tend to settle in fluid soap.

9. As a new article of commerce, aqueous caustic soda, containing sensible quantities of metals normally having a tendency to promote deterioration of soap, which 'caustic soda when reacted with a suitable fatty material will nevertheless produce soap relatively free from such metals, said caustic soda having added thereto a commensurate quantity of an agent selected from the group consisting of the mercaptans and alkali metal sulphides, hyposulphites, thiosulphates, and sulphoxylates.

10. As a new article of commerce, aqueous caustic soda which when reacted with a suitable fatty material will produce soap relatively free from metals tending to promote deterioration of soap, said caustic soda containing sensible quantities of metals which would normally promote such deterioration but which during the interval 'between manufacture and use of said caustic soda have been rendered relatively innocuous and largely precipitated by addition thereto of a commensurate quantity of a sulphur compound which forms with such metals compounds that are relatively innocuous with respect to soap as well as relatively insoluble and tend to settle in fluid soap.

11. As a new article of commerce aqueous caustic soda which when reacted with a suitable fatty material will produce soap relatively free from metals tending to promote deterioration of soap, said caustic soda containing sensible quantities of metals which would normally promote such deterioration, but which during the interval between manufacture and use of said caustic soda have been rendered relatively innocuous with respect to soap and largely precipitated by addition thereto of a commensurate quantity of an agent which will readily give up sulphur to such metals.

12. As a new article of commerce, aqueous caustic soda which when reacted with a suitable fatty material will produce soap relatively free from metals tending to promote deterioration of soap, said caustic soda containing sensible quantities of metals which would normally promote such deterioration, but which during the interval between manufacture and use of said caustic soda have been rendered relatively innocuous with respect to soap and largely precipitated by addition thereto of a commensurate quantity of an agent selected from the group consisting of the mercaptans and alkali metal sulphides, hyposulphites, thiosulphates, and sulphoxylates.

13. As a new article of commerce, aqueous caustic soda which when reacted with a suitable fatty material will produce soap relatively free from metals tending to promote deterioration of soap, said caustic soda containing sensible quantities of metals which would normally promote such deterioration, but which during the interval between manufacture and use of said caustic soda have been rendered relatively innocuous with respect to soap and largely precipitated by addition thereto of 0.1 to 0.8% of sodium sulphide.

14. As a new article of commerce, aqueous caustic soda which when reacted with a suitable fatty material will produce soap relatively free from metals tending to promote deterioration of soap, said caustic soda-containing sensible quantitles of metals which would normally promote such deterioration, but which during the interval between manufacture and use oi said caustic soda have been rendered relatively innocuous with respect to soap and largely precipitated by addition thereto of 0.1 to 0.8% of sodium hyposulphite.

15. As a new article of commerce, aqueous dition thereto of 0.1 to 0.8% of sodium thiom sulphate.

LAUREN B. HITCHCO. ROBERT E. DIVINE. 

